This invention is directed to bending and, more particularly, to bending sheet metal parts.
The production of sheet metal parts is well known. Such parts are used for a variety of purposes. They may be utilized to join longitudinal elements such as stringers and girders end-to-end. They may be utilized to attach girders to stringers, attach sheets of metal to girders and stringers or for a variety of other purposes.
The amount of sheet metal parts produced during a single production run varies from a few to several million, depending upon the industry involved. When the number to be produced in a production run, or a series of production runs, is relatively high i.e., in the order of hundreds of thousands or millions, the production of expensive stamp dies is justified. However, when a smaller number of parts are to be produced i.e., hundreds or thousands, the expense of producing such dies may not be justified. In such instances, other metal bending devices using non-specialized dies are generally utilized. The present invention finds its primary use in such environments.
In the past, limited production runs of parts have usually been made in press brakes using Vee dies and punches by a skilled operator placing the part to be formed in a particular position and then operating a punch. While being versatile, press brakes have a number of disadvantages. First, the whole part is in motion during the bending operation, which makes automatic registration of a second bend extremely difficult. Thus, skilled operators are a necessity. Second, the motion of the part, which is adjacent to the operator, may present a safety problem. Third, conventional tooling is capable of bending in one direction only. Thus, to make a Z-angle or return flange bend, the part or workpiece must be removed from the machine and inverted after the first bend is made in order for the second bend to be made. The end result of these disadvantages is that the production of sheet metal parts utilizing press brakes is time consuming and expensive. Moreover, such machines are relatively unsuitable for automation, primarily due to the complex path through which a part must be moved as it is being formed, particularly when return flange structures are being formed.
Leaf brakes and bar folders have also been utilized to bend sheet metal parts. Because such bending machines maintain one edge of the part stationary during the bending cycle, they are more amenable to automation. However, these bending machines have other disadvantages. Specifically, conventional types of leaf brakes and bar folders create non-uniform bend radii and have a tendency to mark the surface of sheet metal as it is being bent. More specifically, leaf brakes and bar folders bend sheet metal by clamping the metal part between a jaw and a punch (or folding blade) and, then, rotating the clamping structure to bend the workpiece. The rotation pivot point is approximately located at either the center line of the punch radius, or the outer mold line of the part. Because of this location, the rotation action creates a "wiping" motion that often results in the marking of the surface of the part, and a non-uniform bend radius. Thus, while the skill involved in utilizing leaf brakes and bar folders is less than the skill involved in utilizing Vee die press brakes, other disadvantages exist.
Therefore, it is an object of this invention to provide a new and improved sheet metal bender.
It is a further object of this invention to provide a new and improved sheet metal bender suitable for bending sheet metal parts in either direction without requiring that the part be inverted subsequent to bending in one direction.
It is another object of this invention to provide a sheet metal bender that bends sheet metal parts with a minimal amount of marking of the surface of the part.
It is a still further object of this invention to provide a sheet metal bender adapted to bend sheet metal parts such that they have a substantially uniform bend radius.